This invention relates to a method for determining the concentration of deuterium in water. In particular, it relates to the use of this method for estimating the highest temperature that water has attained.
It is helpful in geothermal exploration to determine the highest temperature that a given body of water was subjected to. This temperature affects the deuterium concentration in water; consequently, geothermal data can be obtained by determining deuterium concentration of water which is being investigated.
To measure deuterium concentration by a traditional method, hot uranium or zinc is reacted with water causing hydrogen and deuterium ions to be converted to free elements. The hydrogen-deuterium gas which evolves in the reaction is then analyzed in an isotope ratio mass spectrometer. The first step of the conventional process is expensive, difficult, cumbersome and timeconsuming; the second step lacks in reliability and accuracy because H.sub.3.sup.+ ions, forming in the source, having mass approximately the same as HD.sup.+ ions (one of the principal ions examined by isotope ratio mass spectrometry) interfere with the analysis.
Another approach was to convert a water sample having unknown D.sub.2 O concentration to HCl by reaction with SiCl.sub.4. The HCl was then passed to a mass spectrometer and the ratio of peaks at mass 38 (H.sup.1 Cl.sup.37) and mass 39 (H.sup.2 Cl.sup.37) was determined. Substantial difficulties were encountered, however, in the analysis by mass spectrometer as hydrocarbon impurities contained in water gave a large peak at mass 39.
The present invention obviates difficulties encountered in the process for determining deuterium concentration in water.
Thus, one object of the present invention is to provide a process for determination whether a given sample of water emerged from a geothermal reservoir, i.e., was at one time heated to a high temperature by naturally occurring hot formations near the surface.
Another object of the invention is to provide a process for determining deuterium concentration in water, which eliminates the necessity for complicated extraction of free hydrogen and deuterium from water.
Still another object of the invention is to provide a process for determining deuterium concentration in water, accuracy of which is not affected by the formation of H.sub.3.sup.+ ions during isotope ratio mass spectrometry.
A still further object of the invention is to provide a process for determining deuterium concentration in water, which is rapid, efficient, accurate and inexpensive to perform.
Still another object of the invention is to provide a process for determining deuterium concentration in water, which eliminates the need for sophisticated equipment, intricate operating procedures, and large samples.
Other objects of the invention will become apparent to those skilled in the art upon studying the specification and the appended claims.